A conventional apparatus for deforming an output pulse into a measurable output may be known as an apparatus for detecting a phase current of a motor, in a motor driving apparatus for driving the motor using an inverter.
When the above arrangement is employed, disadvantages arise such that error in current measurement due to ringing, waveform deformation due to extension of pulse output time, scaling in driving range, generation of abnormal sound and the like.
Because no analytic methods were proposed at all for ringing especially, disadvantages arise such that reduction of ringing is difficult, and that rapid response cannot be realized, and that measurement accuracy cannot be improved.
Although it may be considered that a pulse current flowing in a DC link can be detected using a shunt resistor, it is difficult that decreasing in affection of noises and that improving measurement accuracy. And, a disadvantage arises in that current detection cannot be realized other than a long pulse, because of a peak voltage due to inductance of a shunt resistor. Therefore, detecting a phase current using a shunt resistor was not made practicable.